Refractory material and process of making same



Patented Julie I4, 1938 2,120,562

REFRACTORY MATERIAL AND PROCESS OF MAKING SAIWE Clemens A. Laise,Tenafly, N. 1., assignor to Eisler Electric Corporation, Union City, N.J.,' a corporation of Delaware No Drawing. Application Octoberll, 1934,

Serial No. 747,891

16 Claims. (Cl. 75-137) The present invention relates to hard metalmaterial suitable to be used in the extruding compositions, to methodsof working such hard steps hereinafter set forth. The carbidized alloymetal compositions, and to processes for producmay betreated by breakingit up into an abrasive ing compositions of this description that aremetallic powder suitable for directly forming adapted for working intoshapes suitable for hard metal members without the formation of 5 UNITEDSTATES PATENT OFFICE various commercial uses. the extrusion material orthe practice of the ex- Such shapes may take many forms. Among trudingsteps. others may be specifically mentioned the form Under the processesof the prior art, it seemed V of borers for oil-well drilling, sandblast nozzles, to be necessary to produce shapes such as above tips forcutting tools, nibs for wire-drawing dies, described, which might takethe forms of polyg- 10 high resistance insulators for radio circuits andonal, fluted or cylindrical rods or of tubes, by parts and contacts forall types of mechanical machining the same or by pressing or molding andelectrical apparatus subject to extreme wear various types of hard metalcompositions into and tear. I the forms desired, or by first putting thematerial It is an advantage also that the material of into cylindricalform d u sequently shap 15 the invention is practically non-corrosiveand e sa eue, o to the extreme hardmay consequently 'be employed formany uses ness of such materials, it was very difiicult to mawherematerials of the prior art are damaged chine or cut shapes so made, oncethey were by corrosion, tarnish or rust, or by electrolytic ed- This wasParticularly e after the action. Y

I am aware that there are a number of procment which usuallyac'dompanied the pp c esses' for producing hard metal compositions, ofpressure-. some of which include in the composition some of It is n Qbl0f e P es inVehtiOn t prothe basic elements mentioned in the present in-Vide a material and a method of v p g the vention. 'In the past,however, it has been cus- Same that Will p t of as y forming and 25tomary, in making such hard metal compositions, cutting into the desiredShape d Size, and first to provide a finely divided carbid of l. whichmaterial and method greatly increase the fractory metal; then to pressand sinter such Variety Shapes into which hard metal carbide into a formor shape. The resulting positions may be processedform or shape wasnaturally of a rather brittle The invention COmDIBhGHdS a material D 30and porous character but extremely hard. Therecially adapted for th P pabove mentioned, fore, in order to add toughness to the article thesteps of preparing this material, the steps of ,so produced, it wasnecessary to impregnate it shaping the material so prepared into thedesired with a cementing metal. This cementing metal forms and the stepsof hardening the shapes so 3 was introduced into the pressed andsintered carformed into a usable, commercial condition. The bide form orshape, generally either by mixing achievement of these ends is among theobjects the cementing metal in finely divided form with of theinvention. the carbide before pressing and sintering, or else Morespecifically, the invention 'comprehends first pressing and sinteringthe carbide, and then an extrusion material, process and product. The

40 dipping the shape or form into a molten bath of extrusion materialmay be generally described as 40 cementing metal. a refractory metalcomposition in plasticstate;

In contradistinction to these methods and the process includes themixing and alloying, and other similar processes of the prior art, thepresthe carbidizing of. a refractory and a base metal ent inventioncomprehends the mixing, before and the extrusion, drying, baking,cutting and carbidization,- of a refractory metal or metals hardening ofthis material; and the product may 45 with a base metal or metals, bothin very finely be represented by shaped members resulting from dividedform. I have discovered that if such a the application of the process tothe said mamixture' is then heated to a temperature just beterial. lowthat of the sintering temperature of the low- To accomplish these ends amixture is prematerial had been subjected to the heat treat- 20 estmelting point metal in the mixture, there is pared comprising veryfinely divided refractory 50 a relatively rapid combination or alloyingof the metals and. base metals. The refractory metals metal contained inthe mixture. This alloy is should for best results consist of a-mixtureof then very readily carbidized at surprisingly low' any two or more ofthe following: Tungsten, temperatures as hereinafter set forth, andsubtantalum, titanium, zirconium, chromium, thorisequently treated insuch a manner to form a um or rhenium, etc. In fact, any carbide form-55 cedure.

ing metals having a melting point above 1500 C. may be'used. These orsome of these metals of such refractory nature are then in proper casesmixed with one or more of such other metals having a melting point of900 C. or above, as. iron, manganese, nickel, cobalt, silver, copper,etc., also in very finely divided state.

I have discovered that it is possible to produce a remarkable change byintimately mixing and milling finely divided refractory metal powderssuch as tungsten and molybdenum, etc., with base metal powders such asiron, nickel or cobalt, without heating the mixture to the lowestmelting point of any of its constituents. To produce this resultconstitutes the first step in the pro- The mixtureof powders abovementioned is heated in a hydrogen atmosphere in a suitable gas orelectric furnace at a temperature of 700 C. to 900 C. and preferably attemperatures just under the melting pointsof the base metal constituentsfor a period of several hours. Under this treatment a light sinteringtakes place permitting subsequent crushing and sieving; but more thanthis, an apparent absorption of some of the elements into others takesplace, thus forming substantially homogeneous particles having thecharacteristics of alloys. For instance, copper and nickel will readilyintimately intermix in this manner so that a" red 50% mixture, afterheattreating will result in a white or silvery powder no longerresembling the original mixture and having characteristics of an alloy.Similarly, tungsten or cobalt, or tungsten and nickel, may be intimatelyintermixed and alloyed in the powder form. This preliminary intimateintermixing, alloying and sintering stage is, therefore, an importantstep in my process, as it greatly facilitates the preparation of thematerial with which the subsequent extrusion step is carried out.

The next step is the formation of carbides from these intimate mixturesor alloys of metal powders. The sintered alloy metal powders consistmgof refractory metals intimately admixed with base metals, preferably ofthe iron group, are carbidized by uniformly mixing carbon or carbon andboron, also in fine division, with them in order to form a combinationof such alloys with nonmetallic elements such as carbon and boron and tofacilitate theformation of' carbides or borides or both. Such sinteredpowders can be carbidized at temperatures much lowerthan merely thepowdered mixtures of the same composition. 'I'hus, I find to carbldizetungsten powder in itself requires a temperature of 200 C. to 400 C.higher than when I carbidiz'e a. sintered tungsten-nickel alloy powdercontaining 70% tungsten and 10% nickel. The amount of carbon should becalculated to provide an amount sufficient to cause the carbide-formingmetals to absorb .the normal atomic ratio of carbon to metal to give thedesired carbide molecule. The carbon may, however, be added during theheat treatment which follows by heating in an atmosphere of carbonaceousgas. For facility of explanation I shall refer hereinafter to carbides"with the understanding that what is said of. carbides applies equally toborides or carbides and borides. 1

In order to effect carbidization, the alloyed metal powders and carbonare subjected to a heat treatment at a temperature elevated to or almostto the sintering temperature of the mixture and below the melting pointthereof, say 1200 C. to i400 C., for a period of from two to six hours.

pores or voids.

This operation is carried out in a hydrogen, carbonaceous or reducingatmosphere. The result is either a still finely divided productconsisting of carbides, or borides, or, in a case where both carbon andboron are added, of both carbides and borides of the alloyed metals inthe mix. Where the temperature of the heat treat- ,ment is suflicientlyhigh, the powdered metal carcarbidized alloy, however, may be crushedorground to form an abrasive metallic powder which may be used toproduce hard metal members by other methodsthan by the extrusion processherein described.

From this carbidized or boridized fine alloy powder thus prepared, theextrusion material of the present invention is formed and its formationconstitutes the next step.

The nature of this extrusion material is determined by the requirementsnecessitated by the conditions of the extruding procedure which will bedescribed hereafter and, to a certain extent, by atmospheric conditions.

The formation of the extrusion material is best begun by forming a,suitable paste which may act as a binder for the finely divided alloycarbide. This paste may consist of starch, water and ammonia, in theproportions of grams of starch to 825 cc. of water to 75 cc. of ammonia.In place' of the foregoing paste, organic binding materials, such as acaramel solution, gum arabic, or a casein solution, or mineral binders,such as silicates or mineral colloids may be used. In any case thequantity of paste must be such as to render the mixture sufiicientlyviscous so that the extruded mass will hold together into a compact bodyhaving a smooth surface and free from If the mixture of alloy carbidesand paste contains an improper quantity of paste, the extruded piecesmay show minute cracks on the surface. In this case the pieces must bebroken up and remixed'with the proper proportion of paste until theproper consistency for yielding dense, smooth-surfaced products isattained.

The paste may be mixed by the use of any standard heavy duty mixingequipment and should be carried out until a thorough intermixture ofingredients into a plastic mass is obtained. A suitable consistencyhasbeen obtained by mixing refractory carbide powders and a starch pastecompounded as above described in the proportion of about grams starchbinder to 1 kilogram of carbide. The consistency of the composition mayvary slightly under varying atmospheric conditions, but a mixture of thecorrect consistency may be produced under any given set of conditions bya suitable variation in the amount of binder material. In some cases thepaste may be rolled between or under suitable rolls of standard rollingmills so as to render the powders exceedingly fine and the paste hardand plastic so that it must be extruded with the aid of hydraulicpressure.

Extrusion is accomplished by placing this plastic mass obtained as aboveoutlined in an ex.

truding apparatus and forcing the composition and cobalt. This may bestill further hardened through an orifice of suitable shape underhydraulic or other pressure, in excessof one hundred pounds per squareinch. Channels or plates of plaster of Paris or glass may be providedadjacent the extrusion nozzles in order to carry the extruded forms asthey are produced. The extrusion equipment should be kept clean and freefrom. imperfections in order to avoid the formation of scores and faultsin the extruded products.

The next step in the formation of the shaped members of hard metalcomposition characterizing the final product comprises drying theextruded shapes preferably at room temperature and under a slightlyhumid atmosphere for a period of two or three days or longer.

They are then cut to the desired lengths and baked in a sinteringfurnace in order to carbonize the binding material with which theplastic mass was formed. A temperature of 500 to 700 C. for about onehour or less has been found sufficient to carbonize the binding andplasticizing material. The extruded members may be packed in carbonboats surrounded by lamp black during this baking treatment, duringwhich a reducing atmosphere may be maintained to advantage. I

The final step comprises a further heat treatment for bonding togetherthe particles into a uniform, homogeneous, strong. compact.wearresisting body. The carbonized members produced by the bakingtreatment are again packed in carbon boats, surrounded by lamp black,and then heated inan electric furnace at a temperature of 1400" to 1500C This operation is carried out from, 5 to 30 minutes, depending uponthe shape and size of the extruded members. Preferably a carbonaceous orhydrogenous atmosphere is maintained in the furnace during thiscompacting and hardening step.

During the cohesion and adhesion of the particles together under theconditions of the final compacting and hardening step, a considerableshrinkage of the original extruded product takes place, ranging from 10to 30%. Shrinkage in length is generally about 22% and in diameter about27%, although small pieces manifest considerably less shrinkage.Uniformity in shrinkage is facilitated by maintaining as smooth asurface as possible on the extruded members.

An example of the composition of my novel product is as follows:

v Per cent Refractory metal (such as tung sten)- 92.5 to 57.5 Iron .25to' 5 Chromium and thorium .25 to 2.5 'Carbon and boron 5.0 to 10.0Cobalt and nickel "a 2.0 to 25.0

The composition of the starting material is ad- ,iusted with referenceto the additions and losses taking place during the processing, and alsowith the purpose in mind for which the, .end product is to be used. Ifthe final composition is to be exce'edingly hard, the metallicconstituents should be held to a refractory metal content above 90% anda basemetal content below 10%. If, on the other hand, the composition isto be extremely tough,.the base metal content is increased above 10% or12% and the refractory metal content proportionately reduced.

A more specific composition for a superior wear-resisting materialcomprises in its final stage a compact homogeneous body composed of acarbidized alloy oftungsten, chromium, iron.

. group through the incorporation of to 1% of thorium. The final bodyconsists of approximately the following composition:

Cobalt (and/or nickel) 13.5

In cases where a combined carbidizing and boridizing effect is desired,I may add powders of boron suboxide or boron nitride or other suitableboron compounds to the original mixture before the heat treating. andalloying step, or immediately prior to carbidizing. In this case thetotal carbon and boron in the composition should not exceed about 15%.

By the above extrusion process I produce extruded metallic bodies whichare not only exceedingly hard but also exceedingly tough,.the hardnessexceeding on the "A Rockwell hardness scale, and the tensile strengthexceeding 200,000 lbs. per square inch. At the same time my compositionis exceedingly compact and dense. The harder and more compactthe pasteis before extrusion the more dense and pore-free is my composition. Infact, .before extruding, my paste may even be rolled between metallicrolls so as to make the powders exceedingly fine and the pasteexceedingly hard so that it must be extruded on a hydraulic or powerpress.

Having thus described my invention, what I claim is:

1. An extrusion material comprising in a finely divided state acarbidized alloy of two or more refractory metals of the groupconsisting of tungsten, tantalum, titanium, zirconium, chromium, thoriumand rhenium, and a metal of the consisting of iron, nickel, cobalt,manganese, silver and copper, in intimate admixture with a pastecontaining carbonizable material, said paste being present in saidmixture in quantity sufiicient to impart 'to the whole the capability ofbeing extruded through an orifice in the form of a dense, coherent body.

2. An extrusion material comprising a carbidized alloy of tungsten andanother refractory metal with a base metal, said metals being inpowdered form and in intimate. admixture with a' paste consisting ofcarbonizable binding material and water, said paste being present inquantity suflicient to impart to the whole the capability of beingextruded through an orifice in the form of a dense, smooth, coherentbody.

3. An extrusion material comprising a finely divided carbidized alloy oftungsten and another refractory metal with a base metal, said finelydivided carbidized'alloy being in intimate admixture with a pastecontaining carbonizable binding material .and water.

4. The method of making hard metal members comprising intimatelyintermixing finely divided powders of one or more refractory-metals ofthe group consisting of tungsten, tantalum, titanium,

zirconium, chromium; thorium and rhenium,

ganese, nickel, cobalt, silver and copper, sintering and alloying saidmixture and then carbidizing the same, finely dividing the carbidizedproduct,

.thoroughly mixing therewith a paste of carbonizable material andthereby forming said carbidiz'ed material into a plastic mass. extrudingsaid mass into a shape of the desired form, drying the same and cuttingthe dried shapes ap-' powders of one or more refractory metals of thegroup consisting of tungsten, tantalum, titanium, zirconium, chromium,thorium and rhenium, with finely divided powders of one or more basemetals of the group consisting of iron, manganese, nickel, cobalt,silver and copper, sintering and alloying said mixture and thencarbidizing the same, finely dividing the carbidized product and forminga plastic mass thereof, extruding said mass into a shape of the desiredform, drying the same and cutting the dried shapes approximately to.size, carbonizing said shapes and finally firmly cohering the carbonizedproduct.

6. The method of making hard metal members comprising intimatelyintermixing finely divided powders of oneor more refractory metals ofthe group consisting of tungsten, tantalum, titanium, zirconium,chromium, thorium and rhenium, with finely divided powders of one ormore base metals of the group consisting of iron, manganese, nickel,cobalt, silver and-eopper, sintering andalloying said mixture and thencarbidizing the same, finely dividing the carbidized product and forminga plastic mass thereof, extruding said mass into a shape, carbonizingsaid shape and-finally baking the carbonized product under reducingconditions.

7. The method of making hard metal members comprising intimatelyintermixing powders of a refractory metal with powders of a base metal,sintering and alloying said mixture and then carbidizing the same,finely dividing the carbidized product and forming a plastic massthereof, extruding said mass into a shape of the desired form, dryingthe same and cutting the dried shapes approximately to size, carbonizingsaid shapes and finally firmly cohering the carbonized product. o

8. The' method of making hard metal members comprising intimatelyintermixing powders of a refractory metal with powders of a base metal,sintering, alloying and carbidizing the mixture, comminuting thecarbidized product, forming the same into a plastic mass, extruding saidmass, drying the extruded shape, carbonizing the same and finally bakingthe product under reducing conditions.

9. The method of making hard metal members comprising intimatelyintermixing powders of a refractory metal with powders of a base metal,sintering, alloying and carbidizing the mixture, comminuting thecarbidized product, forming the same into a plastic mass, extruding saidmass, drying the extruded shape, carbonizing the same and finallybonding together the carbide particles by heat.

10. The method of making hard'metal members comprising intimatelyintermixing powders of :3.

refractory metal with powders of a base metal, sintering, alloying andcarbidizing the mixture, comminuting the carbidized product, forming thesame into a plastic mass, extruding said mass and then finishing theextruded mass into a hard member of the desired size and shape.

11. The process of making hard metal members which includes the steps offorming a plastic mass of carbidized alloy particles and then extrudingthe said mass.

12. The process which comprises intimately intermixing refractory metalpowders with base metal powders, alloying and carbidizing said mixture,comminuting said carbidized product, then mixing the same with a binderinto a plastic mass, extruding the mass, drying the same, and

- then firmly uniting the mass by heating the same under reducingconditions.

13. The process of making hard metal members which comprises mixing, infinely divided form, one or more refractory metals adapted to formcarbides and having melting points materially higher than 1500 C. withone or more metals also in finely divided state having melting points:above 900 C., alloying said metals by heating said mixture to atemperature of 700 C. to 900 C.,

and rhenium with finely divided metals of the group consisting of iron,nickel, cobalt, manganese, silver and copper, alloying the finelydivided metals in the mixture by heating the same to a temperatureslightly below the melting point of. the metal or metals of the saidsecond group in the mixture, carbidizing the metals thus alloyed,comminuting said carbides, plasticizing the comminuted product, and thenforming the-desired member from said plastic mixture. 15. The method offorming hard metal compositions which comprises intimately mixing andmilling the finely divided metal powders, in dry state, of two or morerefractory metals of the group consisting of tungsten, tantalum,titanium, zirconium, chromium, thorium, and rhenium, and one or moremetals of the group consisting of iron, nickel, cobalt, manganese,silver and copper; then heating the mixture to a temperature below themelting point of the metal or metals of the second group and thereaftercarbidizing the alloy so formed.

16. The method of forming hard metal compositions which comprisesintimately mixing and milling in dry state one or more refractory metalpowders with one or more base metal powders, alloying said metals byheating to a temperature below the melting pointof the base metal ormetals, and thereafter carbidizing the alloys so formed.

CLEMENS A. LAISE.

